1. Field of the Invention
The invention relates in general to a method for detecting the cleanliness of a filter, and more particularly to a method for determining the cleanliness of the filter according to a rotation control voltage received by the fan and an actual rotation rate outputted by the fan.
2. Description of the Related Art
Living in modern age with rapid advance and continual renovation in technology, electronic device has become an indispensable appliance to modern people in their everyday life. The ventilation quality of an electronic device such as desktop computer, notebook computer or projector has much to do with the stability of system operation and the lifespan of the product. Taking the notebook computer for example, in order to ventilate the heat generated by the computer system more efficiently, a computer is normally equipped with a fan to facilitate a normal operation of the computer system under appropriate environmental temperature. Generally speaking, a filter is disposed on an air inlet or air outlet of a fan, wherein the filter can be disposed inside or on the surface of the electronic device, so that the airflow generated when the fan rotates can flow through the filter. Before dusts are accumulated on the filter, the actual rotation rate of the fan corresponds to the rotation control voltage outputted by the central process unit (CPU). That is to say, the CPU outputs a rotation control voltage to the fan, wherein the rotation control voltage corresponds to a pre-set rotation rate which is equal to the actual rotation rate of the fan.
When the fan rotates, dusts tend to deposit on the filter. When too many dusts are deposited on the filter, airflow that flow through the filter will become smaller. Meanwhile, the actual rotation rate of the fan becomes faster than the corresponding pre-set rotation rate of the rotation control voltage. Consequently, the fan will be unable to ventilate the heat outside the electronic device, severely affecting the operation efficiency of the electronic device. Unless the user clean the filter periodically, otherwise it is not easy to be aware that the filter needs to be cleaned or replaced because too many dusts have deposited on the filter. Especially for the filter deposited inside the electronic device, the user cannot gain any knowledge of the cleanliness of the filter just by observing the appearance of the electronic device, unless the electronic device is disassembled and checked. However, such an inspection is very troublesome to the user. How to develop a technology which reminds the user to clean the filter with too many dusts deposited thereon has thus come to the fore.